In recent years, coenzyme Q10 has become widely known to general consumers as supplement or dietary supplement. Coenzyme Q10 is a fat-soluble substance having a quinone structure, and “10” in coenzyme Q10 is derived from the fact that the number of the repeating units of an isoprene side chain is 10. There are two types of coenzyme Q10; oxidized type and reduced type, and oxidized coenzyme Q10 has been widely popularized since oxidized coenzyme Q10 is inexpensive. However, reduced coenzyme Q10 has a higher absorption efficiency, and thus demand for reduced coenzyme Q10 has been increasing.
Conventionally, to obtain reduced coenzyme Q10, a culture method with reduced coenzyme Q10-producing microorganisms is generally used. For example, Patent Literature 1 discloses a method in which microbial cells containing reduced coenzyme Q10 at a ratio of not less than 70 mol % are obtained, and produced reduced coenzyme Q10 is extracted with an organic solvent. Patent Literature 1 also discloses a method in which the reduced coenzyme Q10 is oxidized by an oxidizing agent such as manganese dioxide to produce oxidized coenzyme Q10.